Temperature, pH and carbon source affect drastically indole acetic acid production of plant growth promoting yeasts

Abstract

-Rhizosphere and phylloplane yeasts are able to produce phytohormones, acting as potential plant growth promoters. The aim of this study was to analyze the production of indole acetic acid (IAA) by yeasts using variations in the culture conditions. The yeasts evaluated were Rhodotorula mucilaginosa and Trichosporon asahii, which were cultivated in a potato broth medium with 20 g/L of glucose or sucrose as the carbon source. The cultivation was carried out at 22°C, 25°C or 30°C, and the initial pH was adjusted to 3.0, 4.5 or 6.0. The cultures were analyzed using a colorimetric technique with Salkowski reagent. The cell count was determined in all of the conditions. The results for T. asahii showed that IAA production with sucrose was superior at pH 6.0, and that with glucose was superior at pH 4.5. These results indicate an association between the carbon source and medium pH. Rh. mucilaginosa (2F32) presented a high IAA production when compared with T. asahii (3S44 and 4C06) or even with other microorganisms referenced in the literature. The highest production (0.655 g/L) was obtained at pH 6.0 with glucose as the carbon source. Variations in the culture conditions did not affect the cell growth of the yeasts.

Yeasts producing zeatin

“…It has been reported that both auxin (e.g. Limtong et al, 2014; Streletskii et al, 2016) and zeatin (this study) synthesis in culture varies between species and strains, and may depend on culture conditions (Scarcella et al, 2017). At present, our observations are more relevant for a targeted isolation of yeasts producing plant growth promoters than for plant and yeast ecologists.…”

Rhizosphere yeast Torulaspora globosa with plant growth promotion traits and improvement of the development of tomato seedlings under greenhouse conditions

“…These studies reported an average production of 10.6 g.ml -1 after five days and 45 g.ml -1 after seven days of cultivation, respectively. Thus, our results highlight two important issues related to the production of IAA by yeasts: first, varying results are obtained from diverse strains of the same species, especially if they are isolated from different environments (soil, rhizosphere, or phyllosphere); secondly, the specific conditions necessary for the IAA production, such as sources of nutrients and pH of the medium may influence the production significantly, even preventing it (Apine and Jadhav, 2011;Scarcella et al, 2017).…”

Uji Potensi Isolat Khamir Dari Rhizosfer Mangrove Wonorejo dan Gunung Anyar Sebagai Agen Penghasil IAA (Indole Acetic Acid)

“…Akan tetapi, dalam penelitian ini tidak dilakukan identifikasi terhadap isolat khamir yang digunakan, sehingga tidak diketahui genusnya. IAA pada beberapa jenis khamir berfungsi untuk membentuk filamen yang berguna untuk invasi serta pemanjangan hifa/pseudohifa untuk memperluas daerah penyerapan nutrisi [16]. Contohnya pada Saccharomyces cerevisae, IAA berfungsi sebagai sinyal untuk mengatur filamentasi yang berfungsi untuk invasi.…”

“…Sehingga, ada kemungkinan pada hari ke-4 dan ke-5, sel telah memasuki fase stasioner. Peningkatan produksi IAA pada fase stasioner pada khamir berhubungan dengan menurunnya sumber karbon untuk memenuhi kebutuhan nutrisi bagi metabolisme sel [16].…”